CHICAGO (AP) — A Chicago jury on Friday convicted Oscar winner Jennifer Hudson's former brother-in-law of murdering her mother, brother and 7-year-old nephew in what prosecutors described as an act of vengeance by a jilted husband.

Hudson, who expressed her undisguised disdain for William Balfour when she took the witness stand and who endured weeks of excruciating testimony about the October 2008 killings, was visibly overcome with emotion as the verdict was read. Hudson's eyes filled with tears and she shook her head and bit her lip.

Balfour, 31, faces a mandatory life prison sentence.

Jurors deliberated for three days before reaching their verdict against Balfour, a former gang member who was the estranged husband of Hudson's sister, Julia Hudson, at the time of the triple murders.

With no surviving witnesses to the Oct. 24, 2008, slayings or fingerprints, prosecutors built a circumstantial case against Balfour by calling 83 witnesses over 11 days of testimony. Witnesses said he threatened to kill the entire family if Julia Hudson spurned him.

Balfour's attorneys proposed an alternate theory: that someone else in the crime-ridden neighborhood on Chicago's South Side targeted the family because of alleged crack-cocaine dealing by Jennifer Hudson's brother, Jason Hudson. During the 30 minutes in which they called just two witnesses, however, they presented no evidence to support that theory.

Jennifer Hudson, who was in Florida at the time of the killings, attended every day of the two weeks of testimony, sobbing when photos of her relatives' bloodied bodies were displayed to jurors during closing arguments. Known for wearing tony designer dresses on Hollywood's red carpets, Hudson wore toned-down clothes at the trial, often all black.

Hudson, 30, rose to prominence as a 2004 "American Idol" finalist. But she became a bona fide star for her performance in the film adaptation of the musical "Dreamgirls," for which she won the 2007 Academy Award for Best Supporting Actress.

Hudson was the first witness prosecutors called to testify, and during her more than 30 minutes on the stand she talked about her murdered family members and spoke endearingly about her nephew, Julian King, whom she called Tugga Bear. She said she knew Balfour since the eighth grade but always deeply disliked him.

Balfour had lived in the Hudsons' three-story Englewood home after marrying Julia Hudson in 2006. He moved out in early 2008 after falling out with his wife, but witnesses told jurors he often stalked the home.

The killings occurred the morning after Julia Hudson's birthday, and prosecutors said he became enraged when he stopped by the home and saw a gift of balloons in the house from her new boyfriend.

After his estranged wife left for her job as a bus driver on the morning of Oct. 24, 2008, prosecutors said, Balfour went back inside the home with a .45-caliber handgun and shot Hudson's mother, Darnell Donerson, 57, in the back; he allegedly then shot Jason Hudson, 29, twice in the head as he lay in bed.

Prosecutors said Balfour then drove off in Jason Hudson's SUV with Julian — Julia's son, whom she called Juice Box — and shot the boy several times in the head as he lay behind a front seat. His body was found in the abandoned vehicle miles away after a three-day search.

The defense tried to counter the portrayal of Balfour as an embittered husband by noting Julia Hudson continued to have sex with him until just days before the killings.